EXPONENTIAL LAGRANGIAN CORRELATION-FUNCTION AND TURBULENT-DIFFUSION IN THE INERTIAL SUBRANGE

A simple exponential approximation to the Lagrangian correlation function in turbulent flow has certain desirable properties relating to turbulent diffusion in the inertial subrange. At small time intervals, an exponential correlation function can be approximated by a linear function of time difference; this behaviour is consistent with inertial-subrange expressions for the Lagrangian spectrum and the Lagrangian structure function. Used for turbulent diffusion, the exponential function features inertial-subrange behaviour that clarifies the background of Richardson's 4 3-law and the relation between the dissipation rate and the Lagrangian integral scale. © 1979.